This invention relates to a fiber reinforced composite article and method for making such article. More particularly it relates to such an article and method, for example a composite blading member including an airfoil, having generally angled or transverse pin-type reinforcing members in a toughened and enhanced resin matrix.
Components for sections of gas turbine engines, for example a fan and/or a compressor, operating at relatively lower temperatures than sections downstream of the combustion section have been made of resin matrix composites including stacked, laminated layers. Generally such primarily non-metallic composite structures, which replaced heavier predominantly metal structures, include superimposed layers, sometimes called plies, reinforced with fibers substantially in the plane of the layer. As used herein, fibers include within it meaning filaments in a variety of configurations and lay-up directions, sometimes about a core and/or with local metal reinforcement or surface shielding. For elevated temperature applications, a variety of materials are used for such fibers, including carbon, graphite, glass, metals (forms of which sometimes are called boron fibers), etc., as is well known in the art. Typical examples of such components made primarily of non-metallic composites are reported in such U.S. Pat. No. 3,892,612—Carlson et al. (patented Jul. 1, 1975); U.S. Pat. No. 4,022,547—Stanley (patented May 10, 1977); U.S. Pat. No. 5,279,892—Baldwin et al. (patented Jan. 18, 1994); U.S. Pat. No. 5,308,228—Benoit et al. (patented May 3, 1994); and U.S. Pat. No. 5,375,978—Evans et al. (patented Dec. 27, 1994).
As has been discussed in detail in such patents as the above-identified Evans et al. patent, such non-metallic composites in an aircraft gas turbine engine are subject to damage from ingestion into the engine and impact on components of foreign objects. Such objects can be airborne or drawn into the engine inlet. These include various types and sizes of birds as well as inanimate objects such as hailstones, sand, land ice, and runway debris. Impact damage to the airfoil of blading members, including fan and compressor blades, as well as damage to strut type members in the air stream, has been observed to cause loss of material and/or delamination of the stacked layers. Such a condition in a rotating blade can cause the engine to become unbalanced resulting in potentially severe, detrimental vibration.
The above identified and other prior art have reported various arrangements and structures to avoid such material loss and/or delamination of layers. Some arrangements, for example U.S. Pat. No. 3,834,832—Mallinder et al. (patented Sep. 10, 1974) and the above-identified Benoit et al. patent, include use of seams or fastening devices disposed transversely through a reinforced resin matrix. Their purpose is to avoid delamination of laminated composite structures using, as the composite matrix, ordinary commercial resin systems having the typical relatively low toughness and tensile strain properties. It has been observed, however, that disposition of such ordinary transverse reinforcement with such ordinary resin systems in modem gas turbine engine blading members such as the airfoil of a fan blade and/or without regard to what commonly is referred to in the art as strain energy developed in different portions of a blade airfoil, can result in the above-described type of damage, including delamination and/or material loss. Such damage can reduce the operating integrity and life of a composite article.